In order to improve the productivity and reduce the cost in processing melt-fabricable polymers, extrusion processing at a high extrusion rate is required. Melt-fabricable polymer compositions, however, inevitably have a critical shear rate, and processing at a rate higher than this rate causes a state that a surface is roughened (which is called melt fracture), leading to a failure in providing favorable articles.
One example of methods that can solve such problems, avoid melt fracture, achieve a higher extrusion rate, and improve the extrudability is a method of processing a material at a higher processing temperature. However, high-temperature processing causes pyrolysis of melt-fabricable polymers, which raises problems such as reduction in mechanical properties of articles and staining on articles. In addition, the melt-fabricable polymers are caused to have a lower melt viscosity, and thus drip off or deform before being cooled and solidified. This impairs the dimensional accuracy of articles.
In order to improve the processability in polymer processing, methods of adding a processing aid to a polymer are proposed.
For example, Patent Literature 1 discloses a low-temperature-decomposable engineering plastic having a melting point of 200° C. or lower and a decomposition temperature of 300° C. or lower which can lead to improved processability in processing the low-temperature-decomposable engineering plastic by, for example, reducing the extrusion pressure and the extrusion torque. The literature also discloses a low-temperature-decomposable engineering plastic resin composition obtained by compounding a low-temperature-decomposable engineering plastic and a fluorine-containing resin formed from a fluorine-containing polymer in which a non-terminal carbon atom(s) constituting the main chain is/are coupled with at least one atom selected from the group consisting of a hydrogen atom, a chlorine atom, a bromine atom, and an iodine atom and with a fluorine atom which is substantially free from a polar functional group reactive with the low-temperature-decomposable engineering plastic.
Patent Literature 2 discloses that a chemically resistant fluoropolymer consisting of a fluorinated olefin monomer CF2═CXR1 (wherein X is a hydrogen or halogen atom; and R1 is an alkyl group, for example) and a substantially non-fluorinated olefin monomer CH2═CXR2 (wherein X is a hydrogen or halogen atom; and R2 is, for example, an alkyl group) is used so as to improve the processability of melt-fabricable thermoplastic hydrocarbon polymers.
Patent Literature 3 discloses a processing aid for polyolefins containing an ethylene/tetrafluoroethylene copolymer alone as a fluoropolymer.